On Mon, Jan 15, 2018 at 10:29:46AM -0700, Jens Axboe wrote:
> On 1/15/18 9:58 AM, Ming Lei wrote:
> > No functional change, just to clean up code a bit, so that the following
> > change of using direct issue for blk_mq_request_bypass_insert() which is
> > needed by DM can be easier to do.
> >
> > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> > ---
> > block/blk-mq.c | 39 +++++++++++++++++++++++++++------------
> > 1 file changed, 27 insertions(+), 12 deletions(-)
> >
> > diff --git a/block/blk-mq.c b/block/blk-mq.c
> > index edb1291a42c5..bf8d6651f40e 100644
> > --- a/block/blk-mq.c
> > +++ b/block/blk-mq.c
> > @@ -1696,15 +1696,37 @@ static blk_qc_t request_to_qc_t(struct blk_mq_hw_ctx *hctx, struct request *rq)
> > return blk_tag_to_qc_t(rq->internal_tag, hctx->queue_num, true);
> > }
> >
> > -static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
> > - struct request *rq,
> > - blk_qc_t *cookie)
> > +static blk_status_t __blk_mq_issue_req(struct blk_mq_hw_ctx *hctx,
> > + struct request *rq,
> > + blk_qc_t *new_cookie)
> > {
> > + blk_status_t ret;
> > struct request_queue *q = rq->q;
> > struct blk_mq_queue_data bd = {
> > .rq = rq,
> > .last = true,
> > };
> > +
> > + if (!blk_mq_get_driver_tag(rq, NULL, false))
> > + return BLK_STS_AGAIN;
> > +
> > + if (!blk_mq_get_dispatch_budget(hctx)) {
> > + blk_mq_put_driver_tag(rq);
> > + return BLK_STS_AGAIN;
> > + }
> > +
> > + *new_cookie = request_to_qc_t(hctx, rq);
> > +
> > + ret = q->mq_ops->queue_rq(hctx, &bd);
> > +
> > + return ret;
>
> return q->mq_ops->queue_rq(hctx, &bd);
>
> and kill 'ret', it's not used. But more importantly, who puts the
OK.
> driver tag and the budget if we get != OK for ->queue_rq()?
For the budget, the current protocol is that driver is responsible for the
release once .queue_rq is called, see scsi_mq_queue_rq() and comment in
blk_mq_do_dispatch_sched().
For driver tag, it is released in blk_mq_free_request(), which is done
in failure handling of != OK.
--
Ming
